EP-A 182 333 discloses that the catalyst system Re2O7/γ-Al2O3/SnR4, where R is an alkyl radical, can be used in a metathesis reaction of highly dilute cycloolefin solutions in the liquid phase to give the corresponding cycloalkadienes.
The preparation of cycloalkadienes by a metathesis reaction of cyclooctenylenes having a degree of polymerization of greater than or equal to three and/or cycloalkamonoenes in the liquid phase in the presence of a supported catalyst based on Re2O7/γ-Al2O3 is described in EP-A 343 437.
Many modifications to supported catalysts based on Re2O7/γ-Al2O3, like the additions of dopants have been studied and described in the literature with the aim of improving these catalysts in respect of activity or operating life. The selectivity in respect of the cycloalkadienes to be formed and the total selectivity based on all desired metathesis products, i.e. the sum of desired cycloalkadienes and oligomeric and polymeric metathesis products, is likewise important. Metathesis products, which correspond to downstream products or by-products and are formed from the starting materials not according to plan. For example, ring sizes, which are smaller or larger by one, two or three carbon atoms, are not desired.
GB-1216587 discloses that impregnation of aluminum oxide with anions, for example, with phosphate ions, can increase the activity of the Re2O7/γ-Al2O3 metathesis catalyst.
Metathesis catalysts modified with cesium are known from Journal of Catalysis 1984, 89, 452, and Journal of Molecular Catalysis 1988, 46, 157.
The influence of the treatment of Re2O7/γ-Al2O3 metathesis catalysts with acids is discussed in J. Chem. Soc., Faraday Trans. 1, 1986, 82, 2707.
Due to the necessarily high dilution of the cycloolefin solutions used in the metathesis reaction, the amount of cycloalkadienes, which is obtainable per unit time, has been unsatisfactory from economic, engineering, and industrial points of view.